The movie "Wife of a Spy" is set in Japan in 1940, during the Second World War. The plot centers on Yusaku Fukuhara, a wealthy merchant from Kobe, and his wife Satoko. Yusaku runs an international trading business and is conspicuous for his Western lifestyle and his contacts with foreigners, which makes him suspicious in an increasingly militarized society. Taiji, a childhood friend of Satoko's and now an officer in the Japanese military police, warns Yusaku that he is being watched by the authorities.
Yusaku travels to Manchukuo with his nephew Fumio, officially for business purposes. Upon their return, Yusaku is accompanied by a mysterious woman, which makes Satoko suspicious. She soon discovers that the woman has been murdered and that Yusaku is apparently plotting to escape. Gradually, she learns that her husband witnessed cruel human experiments by the Japanese army in Manchukuo. Yusaku has collected evidence, including a movie and a doctor's notes, to reveal the crimes to the world public. Satoko, who initially believes her husband is an American spy, eventually becomes convinced of his moral motivation.
The situation escalates when Fumio is arrested and tortured by the military police. Satoko, whose loyalty is wavering, hands over incriminating documents to Taiji, which she later regrets. Meanwhile, Yusaku makes plans to secretly smuggle the evidence out of Japan. Satoko decides to support him and accompanies him on his escape attempt. But the military police discover Satoko in a smuggling hideout. However, the film with the evidence was exchanged by Yusaku, so Satoko is released.
In the final stages of the film, Yusaku is shown making a risky escape to Shanghai, while Satoko is committed to a mental institution. When Kobe is destroyed by an air raid in 1945, she manages to escape from the hospital. The epilogue reveals that Yusaku presumably died in the USA, while Satoko also emigrated to the United States years later.
The film tells a gripping story of love, betrayal and moral integrity against the backdrop of an increasingly repressive regime.